save your fla with a new name. comment-out all your actionscript and publish. you'll probably still have a corrupted fla that won't publish.
then delete ~1/2 of your library symbols, resave and publish.
if that succeeds, you've narrowed the problematic object to one of the deleted symbols. either readd the deleted symbols or restart with your original fla and delete ~1/2 of the previously deleted 1/2 and publish.
if publishing fails, delete the other 1/2 and publish.
by successively, deleting ~1/2 of the symbols you should (relatively) quickly find the problematic symbol. when you find that symbol, delete it from your original fla and recreate it. add it to the stage where it previously existed assigning the needed instance names. uncomment your actionscript.